Tinnitus is a medical disorder affecting between 10 and 13 percent of the population. Thus, approximately 36 million Americans and 40 million Europeans suffer from this disorder. Tinnitus can be defined as the sensation of sound perceived in the head or the ear without an evident external stimulus. It is subjective in nature and is a manifestation of malfunction in the processing of auditory signals involving both perceptual and psychological components.
Tinnitus can be triggered anywhere along the auditory pathway. The emergence of persistent annoying tinnitus is usually considered to have psychological components. Tinnitus can be associated with any form of sensorineural hearing impairment, especially difficulty in hearing, ageing and exposure to noise. Middle ear surgery, myringoplasty, chronic supporative otitis media and otosclerosis can all give rise to conductive hearing impairment and tinnitus.
Several alpha2delta ligands are known. Gabapentin, a cyclic alpha2delta ligand, is now commercially available (Neurontin®, Warner-Lambert Company) and extensively used clinically for treatment of epilepsy and neuropathic pain. Such cyclic alpha2delta ligands are described in U.S. Pat. No. 4,024,175 and its divisional U.S. Pat. No. 4,087,544. Other series of alpha2delta ligands are described in U.S. Pat. No. 5,563,175 and U.S. Pat. No. 6,316,638. these patents are incorporated herein by reference in their entirties.